Rocket gas generator for turbofan engine



Oct. 3, 1961 A. M. LANDERMAN ROCKET GAS GENERATOR FOR TURBOEAN ENGINE Filed April 5, 1957 ww kw, MN

Unite Sttes 3,002,340 ROCKET GAS GENERATOR FOR TURBOFAN ENGINE Abraham M. Landerman, Hartford, Conn., assigner to Umted Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed Apr. 5, 1957, Ser. No. 650,909 3 Claims. (Cl. 6035.6)

This invention relates to turbine type power plants and, more specifically, to a combination rocket and air turbojet power plant.

AIt is an object of this invention to provide a power plant of the type described and utilizing a high energy fuel stored in a liquid state yand burned in a gaseous state.

A further object of this invention is to provide an a-ir liqueer wherein the low temperature fuel is passed in heat exchange relation with air lfrom a suitable source. The broad concept -of this type of device is disclosed and claimed in a copending patent application Serial No. 650,913 iiled by Wesley A. Kuhrt as of even date. The present invention in addition to other features further includes a regenerative heat exchanger in which liquid and gaseous air are passed in heat exchange relation.

it is a further object of this invention to provide a rocket chamber which discharges gases through a turbine which in turn discharges into a main combustion chamber. Means is also provided yfor two variable area exhaust nozzles in series.

These and other objects of this invention will become readily apparent from the following detailed description of the drawing, in which:

FIG. l is a partial cross section and partial schematic illustration of the power plant cycle of this invention, and

FIG. 2is an enlarged detailed cross section of a typical variable stator vane turbine construction.

Referring to the drawing, a power plant is generally indicated at lt) and includes an inner body 12 which has a conical leading edge spike'14 which cooperates with an outer casing .16 to define an annular passage 18. Theannular passage 18 has an inlet 20 at the upstream end thereof which leads to a compressor or fan 22. The inner wall 24 formed by the inner body 12 includes a passage 26 for bleeding off boundary layer air and `emitting this air through suitable hollow rstreamlined struts 28 through the exits 30 leading outboard of the power plant. The inner body y12 carries the compressor 22 and extends aft thereof forming a chamber 34 which houses a plurality of primary rocket type combustion chambers 36 which exhaust gases into the turbine 38 which drives the compressor 22 via a gear box 40. The gases exhausted from the turbine 38 pass through a nozzle 42 having movable elements 44 for varying the area of the nozzle 42. The area may be varied by any suitable mechanism, as, yfor example, that shown in Patent No. 2,714,285. Gases emitted `from the exhaust nozzle 42 pass to 4a main combustion chamber 48 where the gases mix with the air coming from the compressor 22 and are burned adjacent the ameholders 50. The ameholders 50 are combined with fuel spray bars 51 which discharge fuel in the gutters formed by the V-type flameholders. Downstream of the main combustion chamber is a convergent-divergent nozzle 52 which may include mov-able members 54 for Varying the area of the nozzle 52. The members S4 may be moved for varying the area of the nozzle by any suitable means Ias, for example, shown in Patent No. 2,714,285 mentioned above.

As seen in FIG. 2, the tur-bine 38 has nozzles upstream thereof which nozzles are formed by stator vanes 55. The vanes S are pivoted at 56 and carry arms 57 which can be simultaneously moved by a ring 58 to vary the angle of the blades. This motion will vary the 'geometry of both the throat and exit area of the nozzles formed by the vanes 55. The throat of the nozzles formed by the vanes 55 is -varied so that the combustion chamber pressure is held constant as the flow through the main part of the power plant changes during flight.

With variable stator vanes 55, the nozzle 42 may or may not be of variable area.

Referring again to FIG. l, the fuel for the power plant is preferably a high energy fuel such as hydrogen which is stored in a liquefied state in a suitable container 60. Liquid hydrogen from the tank l60 is pumped by means of a high pressure pump 62 through small diameter tubes 72 of a main heat exchanger 64 where the hydrogenis heated and passed through a conduit 66. Some of the Afuel passes directly lfrom pump y62 to line 66 without going through the heat exchanger tubes 72. The amount which bypasses the heat exchanger may be regulated by the valve 63.

From line 66 the fuel flows through coils 65 which surround the combustion chamber or Iafterburner 48 for cooling the yafterburner. After leaving the coils 65 the fuel is divided by a Valve 67 so that some of the fuel hows directly to the 4fuel spray bar 51. The remaining then flows to the rocket type combustion chambers 36. The other heat exchange medium of the heat exchanger 64 is precooled gaseous air which is conducted to the conduit 70 around the tubes 72 to -a liquid air pump 74. The precooled air from the conduit 70 is liquefied in the heat exchanger 64 lfrom whence it is pumped by the liquid air pump 74.

Liquid air flows through the line 76 to a regenerative or precooler type of heat exchanger 78 where it is gasi- -iied and then passes in a gaseous state through the lines 30, 82 to the rocket type combustion chambers 36 where it combines with the heated hydrogen fuel. The second medium passing through the regenerative heat exchanger '78 is gaseous air which is tapped olf from the main power plant duct downstream of the compressor 22 and passes to the line 86 which leads around tubes 38 of the regenerative heat exchanger 78. The precooled air from -around the tubes 88 then passes to the line 70 and the main heat exchanger 64 in the manner described above.

The mixture of hydrogen and gaseous air leading to the rocket type combustion chambers 36 is fuel rich so that an excess of hydrogen appears in the gases being emitted from the exhaust nozzle 42 immediately downstream of the turbine 38. The surplus of hydrogen then mixes with the air which is owing from the compressor 22 via the annular chamber 90. The air and the `gases emitted from the nozzle 42 are subsequently burned in the main combustion chamber 48 and then emitted from the convergent-divergent nozzle 52.

As a result of this invention, it will be apparent that a high output power plant has been provided which is low in weight and has an extremely low specific fuel consumption. Furthermore, higher oxidizer to fuel ratios are obtained in the gas generator which results in a temperature rise which makes for better combustion characteristics. Because of the higher turbine inlet temperatures less fuel is required to drive the turbine and in many cases it allows `for operation at a reasonable afterburner temperature without having excess fuel in the afterburner combustion products. As a result, the thrust specific fuel consumption will also be improved.

By using compressor bleed air rather than ram air for the liquefying source, the engine has better sea level static take-olf capability. Also, the precooler is more eective than an expansion turbine because it cools the bleed air more effectively without excessive pressure drops. The pressure drop is a very important consideration when designing the main heat exchanger and plays an important part in avoiding any possible cavitation problems in the liquid air pump.

Although only one embodiment of this inventio-n has been illustrated and described herein, it will be apparent that various changes and modications may be made in the construction and `arrangement of the various parts without departing `from the scope of this novel concept.

What it is desired to claim by Letters Patent is:

1. In a turbine type power plant including an air intake, an axial flow compressor receiving air from said air intake, a main combustion chamber receiving air from said compressor, a sou-Ice of hydrogen fuel in a liquid state, an air-to-air regenerative heat exchanger, an air-to'- fuel main heat exchanger in series flow connection with said regenerative heat exchanger, means for conducting a part of the air from the discharge end of said compressor to said regenerative heat exchanger to precool said air, means for conducting said precooled air immediately to said main heat exchanger to liquefy said air and to heat said fuel, means for conducting said liquid air to said regenerative heat exchanger to precool the gaseous a-ir from said compressor and gasify said liquid air, a primary combustion chamber having a primary exhaust nozzle upstream of said main combustion chamber, means for conducting gaseous air from said regenerative heat exchanger and an excess of fuel from said main heat exchanger to said primary combustion chamber, a turbine receiving the gases produced by said prima-ry combustion chamber for driving said compressor, and means for mixing the exhaust gases from said turbine and the air lfrom said compressor for burning in said main cornbustion chamber including means for injecting `fuel from said source into said main combustion chamber.

2. In a turbine type power plant including an air intake, said power plant comprising an outer casing and a central body forming inner and outer walls which define an annular duct, means downstream of said inlet for Ibleeding boundary air from along at least one of said walls and discharging said ow overboard of the power plant, a compressor in said duct receiving air from said inlet, a main combustion chamber adjacent the downstream end of said central body, a main exhaust nozzle downstream of said combustion chamber and downstream of the downstream end of said inner body, means for varying the area of said main exhaust nozzle, a source of hydrogen fuel in a liquid state, a regenerative heat exchanger, a main heat exchanger, means for conducting fuel from said source through one of said heat exchangers, a source of air, means `for conducting `air from said source through both of said heat exchangers in series whereby one exchanger is in an air-to-air heat exchange relation and the other exchanger is in a fuel-to-air heat exchange relation, a rocket combustion chamber receiving an excess of fuel from one of said heat exchangers and air from the other heat exchanger, a turbine receiving gases only from said rocket combustion chamber and driving said compressor, a second exhaust nozzle downstream of said turbine and upstream of said main combustion chamber and exhausting gases into said main com-bustion chamber for mixing wit-h the air from said compressor, and means for conducting fuel from said source to said main combustion chamber including a heat exchanger adjacent said main combustion chamber.

3. In a turbine type power plant including an air intake, said power plant comprising an outer casing and a central body forming outer and inner walls, respectively, which deiine an annular duct, means downstream of said inlet Ifor bleeding boundary air from along said inner wall and discharging ,said flow overboard of the power plant, a compressor in said duct receiving air from said inlet, a 4main combustion chamber adjacent the downstream end of said central body and 'forming a continuation of said annular duct, a main exhaust nozzle downstream of said corn-bustion chamber, means for varying the area of said main exhaust nozzle, a source of hydrogen fuel in a liquid state, a regenerative liquid air to gaseous air heat exchange-r, a main liquid fuel-to-air heat exchanger, means for conducting fuel from said source through `said main heat exchanger, a source of air comprising a duct receiving air from the discharge end of said compressor', means for conducting air from said source through said regenerative heat exchanger then through said main heat exchanger and then back through said regenerative heat exchanger in succession, a rocket combustion chamber upstream of said main combustion chamber and carried by said central body, said rocket combustion chamber receiving an excessive amount of fuel trom said main heat exchanger and air vfrom said regenerative heat exchanger, a turbine receiving gases only from said rocket combustion chamber and driving said compressor, a second exhaust nozzle at the downstream end of said central body and upstream of said main com-bustion chamber and exhausting gases into said main combustion chamber for mixing with the air from said compressor, and means for varying the area of said second exhaust nozzle.

References Cited in the tile of this patent UNITED STATES PATENTS 2,219,994 Jung Oct. 29, 1940 2,563,270 Price Aug. 7, 1951 2,672,726 Wolf et al. Mar. 23, 1954 FOREIGN PATENTS 736,486 Germany June 18, 1943 749,009 Great Britain May 16, 1956 

